Aerodynamic Investigation by Computational Fluid Dynamics to Exterior Design Modifications in a Simplified Bus Model

Exterior design modifications have crucial importance on vehicle aerodynamics. Therefore, it makes one of the key parameters to achieve to reduce the fuel consumption in diesel-, CNG-, and hybrid-powered engines and increase the range of electric vehicles (EVs). The slightest change in the vehicle exterior design can directly affect the vehicle aerodynamics. Thus, four different parameters (front windshield angle, front diffuser angle, rear diffuser angle, and fillet [bending] on the rear and front top) are reviewed on a conceptual 12 m long bus which is to be designed at Anadolu Isuzu. Computational fluid dynamics (CFD) simulations become a source for comparative evaluations in these studies. Simulations are carried out for all different models with a realizable k-epsilon turbulence model and enhanced wall treatment wall function. In conclusion, a positive aerodynamic effect is observed with parameters that are the windshield, front diffuser angle, and fillet on the rear and front top ends. On the other hand, a negative aerodynamic effect is observed when rear diffuser angle is applied. All simulations are compared based on drag coefficient values. The front windshield angle is found the most influential parameter on a conceptual vehicle design that can be provided a drag coefficient reduction of up to 51%.